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The Bay Area water system does not pose a significant threat to human health, even after an increase in contaminants due to the recent drought.

Trihalomethane, or THM, levels have been increasing in East Bay drinking water for the last few years, according to a report released in June 2017 by the East Bay Municipal Utility District. THM, which can lead to increased risk of cancer in certain high amounts, according to campus public health lecturer Charlotte Smith, is a contaminant that occurs in water systems.

Because the Bay Area water source is in the Sierra Nevada and is a protected watershed, there are no industrial pollutants in the water, but there are microbes that cause the formation of THM when they bind with chlorine, Smith said.

“Animals are going to defecate, birds are going to drop bird droppings into the reservoirs,” Smith said. “Operators will add chlorine. The chlorines bind with small organic molecules. … That product we call a disinfection byproduct. THM is the most common.”

The THM levels have returned to normal after their increase in the wake of the drought in the East Bay over the past few years, meaning they are no longer a threat, according to Smith. She added that THM is only carcinogenic at certain high levels.

Campus environmental engineering professor emeritus Alexander Horne said that during the drought, the organic matter in the water increased, causing THM levels in the East Bay Municipal Utility District water system to increase.

Horne also concluded, however, that the drinking water in the Bay Area is relatively safe.

“By and large, our drinking water quality is very good,” Horne said. “The Bay Area water situation is better than most.”

Like THM, mercury can also be a problem as it contaminates fish that are later consumed by humans. While mercury is a problem in the San Francisco Bay, it isn’t too bad unless it occurs in very high quantities, according to Horne.

Horne added that the Bay does have some mercury — a problem that state officials are currently working to solve.

“We’ve come a long way in treating wastewater,” Horne said. “The question is how much farther do we have to go.”

Smith said any problems the Bay Area does face in terms of water pollution should be addressed through the California State Water Resources Control Board.

Environmental protection has become a political issue, according to Smith, and though statewide water regulations are well-enforced, questions remain about what will happen on a federal level under President Donald Trump’s administration.

Smith added that citizens have a responsibility to maintain the quality of Bay Area water and that when signs say “Do not dump in storm drains; it goes into the Bay,” people should respect them.

“We’re lucky to live in California, where the regulations related to drinking water … are stringent and well-enforced,” Smith said. “It’s important that regulations aren’t loosened and that the citizens remain diligent to keep an eye on the regulations.”